It has been known that organic materials such as thermoplastic resin, thermosetting resin, natural or synthetic rubber, mineral oil, lubricating oil, adhesive, paint, etc. are deteriorated by an action such as heat, oxygen, etc. on production, processing and use to cause deterioration of the strength of the organic material due to a phenomenon (e.g. molecular cleavage, molecular closslinking, etc.), change in flow properties, coloring, deterioration of surface physical properties, etc., which results in decrease of a commercial value. It has hitherto been known that the organic material is stabilized by containing various phenol and phosphorous antioxidants for the purpose of solving these problems about heat deterioration and oxidization deterioration.
As the phosphorous antioxidant, for example, tris(2,4-di-t-butylphenyl)phosphite is used.
However, these known phosphorous antioxidants had a problem that the stabilizing effect to heat deterioration and oxidization deterioration is insufficient.
On the other hand, as those for solving the problem of the phosphorous antioxidant, there is suggested, for example, a cyclic phosphite having a phenolic hydroxyl group, such as 2,10-dimethyl-4,8-di-t-butyl-6-{2-3-(3-t-butyl-4-hydroxy-5-methylphenyl)p ropionyloxy!ethoxy}-12H-dibenzod,g!1,3,2!dioxaphosphosine, etc. (JP-A-5-86084).
The present inventors have produced various phosphorous compounds and studied intensively. As a result, it has been found that specific cyclic phosphites having an alkoxy group or an aralkyloxy group in place of the phenolic hydroxyl group shows not only excellent discoloration-resistant effect but also excellent stabilizing effect which is the same as or superior to that of the cyclic phosphites having the phenolic hydroxyl group. Thus, the present invention has been accomplished.